The present invention relates to a method for determining disturbed and/or occupied frequency channels in a mobile communication system wherein after registration of a mobile telephone to a testing apparatus measurement report parameters between the mobile telephone and the testing apparatus in frequency channels to be probed are detected and evaluated. Further, the present invention relates to a testing apparatus, in particular for implementing the above method.
In order to check functions of mobile or cellular telephones for being in accordance with specifications necessary for operation in the net, it is known to test the mobile telephone using a testing apparatus. In single frequency channels of the net characteristic RF or HF parameters so called measurement report parameters of the mobile telephone are measured which can be used in order to find out whether the functions of the mobile telephone are in accordance with the specifications or whether a defect is present. Disturbed, distorted and/or occupied frequency channels which can temporarily be disturbed, distorted and/or occupied or disturbed, distorted and/or occupied during the entire measurement, externally impair the measured measurement report parameters of the mobile telephone and, therefore, can corrupt the measurement data. In this way the obtained data appear as if a defect is present although the mobile telephone is free of any malfunctions. Such measurement artifacts can be recognized and can be excluded from the measurement when in addition to the conventional testing apparatus spectrum analyzers are used for determining distorted and/or occupied frequency channels in the local communication net. However, the use of spectrum analyzers for measuring net properties has a plurality of drawbacks. In particular, it has to be noted that spectrum analyzers are quite expensive and complicated to use. Especially for small service and/or repair shops it is almost impossible to profit from the benefits of such a spectrum analyzer measurement.
It is an object of the present invention to avoid the drawbacks of the prior art and in particular to provide a method for determining disturbed and/or occupied frequency channels wherein in a cheap and easy way for a particular geographical point disturbed and/or occupied channels of the local communication net can be determined.
It is another object of the present invention to avoid corrupted measurement values when testing mobile or cellular phones without having the need to provide an expensive spectrum analyzer.
The above objects are solved by the invention, and more precisely by detecting a measurement report parameter in each channel in the frequency channels to be probed using a suitable high frequency level and by comparing it in a comparison procedure to a threshold value wherein the probed or measured channel is recognized as disturbed and/or occupied when there is a significant difference between the measurement report parameter compared to the threshold value.
In particular, a certain measurement report parameter of the mobile telephone is selected, the behavior of which relating to a preset threshold value in the respective probe channels provides hints or information regarding disturbances or interferences in the respective channels. The step of comparing the measurement report parameters to the threshold value (or interval) is thereby started anew in the respective frequency channels to be measured. In case a deviation or difference is present in the respective channels the corresponding channel in which a difference is detected and the corresponding value of the difference of the parameter is stored and thus available. By storing the parameter which is changed from a reference value characterizing an undisturbed state and by storing the corresponding frequency channels, disturbed and/or occupied channels are unambiguously determined without the need of using an additional spectrum analyzer. Thus, artifacts due to disturbed channels can be avoided when testing the functions of mobile or cellular telephones.
According to a user-friendly variation of the invention the detected channel(s) and/or the detected measurement report parameter(s) and/or its deviation(s), respectively, is stored when there is a significant deviation of the measurement report parameter compared to the threshold value in a certain channel. In this way, a reference and a further use of the information about the local communication net obtained by the method according to the invention is available.
Preferably, the stored measurement report parameters are displayed as a function of the respective probed channels so that using such a spectral distribution disturbed and/or occupied channels are visually detectable in an easy manner.
Preferably, a suitable measurement report parameter is selected for the channels to be probed or scanned. Such a measurement report parameter can, in particular for a certain frequency band, be preset or can be determined dependent on further criteria for a measurement.
According to a preferred embodiment of the method according to the invention as a threshold value the expectation value of the selected measurement report parameter in the respective frequency channels can be used inasmuch as the expectation value of such a parameter is an average value present in an operation without disturbances, such as interference, distortion, occupation.
According to another preferred variation a parameter is selected which comprises information about the bit error rate and is used as the measurement report parameter. In particular, for GSM/PCN/PCS nets (GSM: global system for mobile communication; PCN: personal communication network; PCS: personal communication system) the RXQUAL parameter is selected as a measurement report parameter comprising the information about the bit error rate. Thereby, a particularly sensitive method can be realized because there is a relatively precise correlation between the HF or RF level offered by the testing apparatus and the measurement report parameter RXQUAL retransmitted from the mobile telephone. The RXQUAL values show a significant deviation from the expectation value of an undisturbed channel even when interferences are low.
As an alternative, which also provides sufficient sensitivity as a measurement report parameter a parameter is selected which comprises information about the reception level. In GSM/PCS/PCN nets as a measurement report parameter the RXLEV parameter is selected, inasmuch as also in case of the RXLEV parameter there is a correlation between the RF level offered by the testing apparatus and the RXLEV value retransmitted from the mobile telephone.
It is noted that RXQUAL is an abbreviation and stands for Radio Link Quality/Received Signal Quality. Further, RXLEV is an abbreviation and stands for Received Signal Input Level. The RXQUAL parameter measures reception quality and the RXLEV parameter measures reception level. It is not known in the prior art to use these parameters to scan the local conditions of a communication net using a cellular phone and a tester therefor.
In particular, for sampling or probing temporary disturbances or interferences and in order to further increase the sensitivity of the method, the channels to be measured are sampled a plurality of times. Thereby, when sampling a plurality of times, the detected values of the selected measurement report parameter are added channelwise. In case of the RXQUAL parameter the added RXQUAL values per channel result in a relative measure of the field strength of the disturbance inasmuch as the numerical value of the RXQUAL parameter is increased with the level of the disturbance.
In case of stronger disturbances it is preferred in order not to lose the control over the process of switching channels to respectively set the high frequency level high when switching between the channels to be probed and lower when detecting the measurement report parameters in the channels to be measured. According to a particular preferred embodiment the detecting of a measurement report parameter is carried out with a low RF level of about xe2x88x9290 dBm. According to a particularly useful embodiment of the present invention the registration of the mobile is made in the lowest frequency channel of a frequency band. Therein, the channels of the frequency band are measured channelwise using a measurement loop.
According to another embodiment of the present invention the channels which have been recognized as disturbed or occupied are blocked. In this way automatically an erroneous measurement or check of the mobile telephone can be avoided. As an alternative or in addition thereto warning messages can be displayed comprising information about the charnels recognized as disturbed and/or occupied. This is in order to inforn the user of the testing apparatus that wrong measurements are probable with these channels.
According to another aspect of the present invention the above stated object is solved in that the testing apparatus comprises means for determining disturbed and/or occupied frequency channels of a mobile communication net.
Further, the invention provides means for comparing the respective detected measurement report parameters to a threshold value and means for storing and displaying the measurement report parameters detected in the probed channels. Further, the testing apparatus comprises means for adjusting the RF level wherein a RF level as high as possible can be adjusted for switching channels and wherein the RF level can respectively be lowered for a detection of a measurement report parameter. Further, the apparatus may comprise the means for setting all the channels.
Thus, according to the invention, disturbed and/or occupied channels can be detected and displayed without the need to use an additional spectrum analyzer. Corrupted measurements due to disturbed and/or occupied channels which result in measurement artifacts of measurement of one or more device functions of a mobile or cellular telephone can be avoided.
Further preferred embodiments of the invention are disclosed in the dependent claims.